I own a 2005 BMW X3 3.0i with an automatic transmission and 108k miles on the odometer. Over the last few months the X3 has developed what I would describe as a slight hesitation or jerking sensation at highway speeds. The hesitation is only noticeable at highway speeds when climbing a large hill or incline. If I press the gas pedal when motor starts to hesitate the RPM's will increase, transmission changes gears and the hesitation immediately goes away. If I slightly decrease pressure on the gas pedal the load is removed from the motor, transmission remains in the same gear and the hesitation goes way. In my opinion, the hesitation doesn't feel like a slipping transmission, because the hesitation immediately goes away if I press or decrease the fuel pedal. The PRM needle also slightly bumps or fluctuates up and down when the hesitation is taking place. Once I go faster or slower the RPM's will level out and remain constant. I took it to my local independent shop on Monday of this week and they said they could not reproduce the hesitation and no codes were thrown. I did replace the sparkplugs around 10k miles ago with Bosch Platinum 4 sparkplugs from Bavarian Auto. These are the 5 dollar plugs compared to the 21 dollar BMW sparkplugs. I don't know if the sparkplugs would cause hesitation at highway speeds. I just ordered a new fuel filter. Unfortunately, the filter is in the tank, but I am going to give it a shot. In the event that the fuel filter does not correct the hesitation does anyone else have any suggestions on a possible cause? Thanks!
Try putting the original Bosch spec plugs back in Auto parts stores try to hype platinum plugs whenever possible because there's a higher profit margin on platinum plugs, not because they're necessarily better plugs. Most engines don't deliver a hot enough spark to deliver any measurable performance benefit from platinum plugs. You might also want to try finding another spark plug supplier. I checked Bavauto and was astonished to see them priced at 21.95. There's got to be a better price than that.
I swapped out the aftermarket sparkplugs for the expensive BMW plugs. Unfortunately, the hesitation still exists. I am dropping her off at another independent shop in the morning, so I am hoping they can diagnosis the problem.
